This invention relates to systems for magnetically-assisted surgery and more particularly to systems for producing the magnetic fields required to guide surgically implanted magnetic medical devices.
Several magnet systems to provide guidance for magnetic medical devices for navigation within a patient have been devised or are under development. An example of such a system is disclosed in commonly assigned application Ser. No. 09/189,633, xe2x80x9cArticulated Magnetic Guidance System,xe2x80x9d which is hereby incorporated by reference in its entirety. A device disclosed therein includes a bed, a bed articulation system, a pair of x-ray sources, a coil or magnet articulation system, and an optional pair of additional magnets. The magnet articulation system comprises an articulation support, servo control mechanisms to provide movement of a coil or a permanent magnet along an arcuate arm both through a polar angle and in a radial direction. Optionally, the entire arm may also be pivoted through an azimuthal angle. The arm itself may comprise a track and gimbal assembly. Additional embodiments described in the referenced application include one in which the arm itself is moveable via an articulation support, another in which the magnet or coil is mounted on a pivotable ring support, and another in which the magnet or coil is mounted as an effector on a robotic arm. In the latter embodiment, it is desirable for the effector and all other parts of the robotic arm to be provided with exclusion zones to prevent accidental contact with a patient, with medical personnel, and, of course, with other items that might be damaged by such contact.
Other magnetic systems that provide guidance for magnetic medical devices within a patient are disclosed in commonly assigned application Ser. No. 09/211,723, filed Dec. 14, 1998, xe2x80x9cOpen Field System for Magnetic Surgery,xe2x80x9d which is also incorporated by reference in its entirety. A plurality of magnets are configured and arranged to provide a magnetic field effective within an operating region of a patient to navigate a magnetic medical device within the operating region while providing access to the patient for imaging and other purposes. A single magnet is arranged and configured to provide a magnetic field along at least one of a plurality of oblique axes extending through the operating region. One or more magnets are arranged and configured to provide a magnetic field along each of the other of the oblique axes. The magnetic fields generated by the magnets are effective to controllably navigate the magnetic medical device within substantially the entirety of the operating region. A preferred embodiment of the system described in this reference comprises three magnets in three mutually perpendicular planes, arranged so that their axes at least converge and more preferably intersect in the operating region. The magnets are arranged in an open configuration, so that the patient typically does not have to extend through a magnet coil to reach the operating region. In a preferred embodiment, the magnets comprise coils that are fixed with respect to one another in a generally downwardly facing hemispherical shell.
Still other magnetic systems providing guidance for magnetic medical devices navigated within a patient are disclosed in commonly assigned Provisional App. Ser. No. 60/095,710, filed Dec. 14, 1998, xe2x80x9cMethod and Apparatus for Magnetically Controlling Catheters for body Lumens and Cavities,xe2x80x9d which is also incorporated by reference in its entirety. The apparatus of the invention disclosed therein generally comprises a magnet system for applying a magnetic field to a magnet-tipped distal end of a medical device. The magnetic field provides a field that can navigate, orient, and hold the distal end of the medical device in the body. The apparatus also includes a computer for controlling the magnet system. Imaging devices connected to the computer provide images of the body part through which the catheter is being navigated. Displays are provided of these images. A controller connected to the computer has a joystick and a trigger to enable a user to input points on the displays for two-point and three-point navigation. The magnet system itself is preferably a set of electromagnetic coils that can be disposed around the body part to create a magnetic field of variable direction and intensity. Magnet systems suitable for such use are disclosed in U.S. Pat. Nos. 4,869,247, issued Sep. 26, 1989, xe2x80x9cVideo Tumor Fighting System,xe2x80x9d and 5,125,888, issued on Jun. 30, 1992, entitled xe2x80x9cMagnetic Stereotactic System for Treatment Delivery,xe2x80x9d the disclosures of both of which are also incorporated by reference in their entirety.
In the commonly assigned application entitled xe2x80x9cDevice and Method for Specifying Magnetic Field for Surgical Applications,xe2x80x9d application Ser. No. 09/020,798, filed Feb. 9, 1998, and which is hereby incorporated by reference in its entirety, six normally conducting or superconducting coils are arranged in a rectangular box or helmet. With the Z-axis defined in the direction of the axial component of the head, the X- and Y-coil axes are rotated 45xc2x0 from the sagittal plane of the head. Biplanar fluoroscopy cameras linked to a real-time host system are provided. Both cameras are calibrated to the six-coil host helmet design, in which three pairs of opposing coils on mutually perpendicular axes are provided. X-ray generators are also provided for the cameras.
In yet another commonly-assigned application entitled xe2x80x9cMethod and Apparatus Using Shaped Field of Repositionable Magnet to Guide Implant,xe2x80x9d application Ser. No. 09/020,934, filed Feb. 2, 1998, and which is herein incorporated by reference in its entirety, an apparatus comprising a moveable magnet assembly having a plurality of fiducial marks is disclosed. In an exemplary embodiment, the magnet assembly may be a gantry supporting either a strong permanent magnet or a superconducting electromagnet, although a strong permanent magnet may require additional articulation to compensate for its lack of current control and magnitude. The magnet assembly may be automatically controlled to provide the needed orientation, location and coil current required to align its magnetic field with the desired motion of a magnetic object to be guided. Localizers and camera-like sensors are provided to detect the fiducial marks on the magnet assembly, and additional fiducial markers may be placed on the patient""s body. Medical imaging devices are used to display the location of the magnet relative to the volume of interest in the patient and the location of the implant. Various means are provided for moving the magnet.
Each of these devices and methods provides some success in being able to provide magnetic field orientations in all directions in sufficient strength for the intended applications. Nevertheless, even with specially designed systems, it is still difficult to completely avoid interference with the imaging system while achieving full functionality of the magnetic guidance system. In many of the above systems, this difficulty becomes apparent in the requirement to provide limitations in the movements of one or more large magnets or their supporting structures, or in limitations imposed on movements and positioning of an imaging system relative to the magnet system. In addition, the systems designed to date, including many of the above, have been quite large and expensive, or are restricted in purpose and application.
It would therefore be desirable to provide a relatively inexpensive system for magnetically assisted surgery that could produce a magnetic field in any orientation and at sufficient strength for use in medical applications. It would also be desirable if the system could provide field lines through a given procedure point in space (i.e., the location of the magnetic medical device) that could be easily and safely changed with a minimum of articulation of the magnet, so that the effect of the various exclusion zones in an operating region could be minimized.
The system for magnetically assisted surgery of a patient of this invention comprises a magnet support structure, a patient support structure, and a multipole magnet attached to the magnet support structure so that the magnet provides a near-field magnetic field in an operating region within a patient supported by the patient support structure. The magnet is moveable to alter the direction of magnetic field lines in the operating region of the patient. The magnet is preferably a quadrupole magnet, and may be a permanent magnet.
If the magnet is a permanent quadrupole magnet, it is preferably cylindrical, comprising a pair of essentially semicircular segments joined so that the segments attract each other strongly in a highly stable arrangement. This arrangement would provide, in a region near a face of the magnet disk, a magnetic field essentially parallel to the face of the magnet disk, along the axis of the magnet. The magnet may be mounted so that it can be rotated on its axis and/or translated in one or more radial directions. A medical imaging system may also be provided and configured to provide a medical image of the operating region of a patient.
In accordance with a second aspect of the invention, a system for magnetically assisted surgery of a patient comprises a magnetic medical device configured to be implanted in a patient, a patient support structure, a magnet support base, and a magnet assembly adjustably supported on the support base and positionable thereon to provide a magnetic field of specified magnitude and direction and having a transverse gradient at the location of the magnetic medical device within the patient supported by the patient support structure. The magnet assembly may comprise a computer-controlled robotic arm having a magnetic effector, and the system may further comprise a medical imaging device configured to provide a relative location and orientation of the magnetic medical device in the patient and of the magnet assembly. The magnet assembly may itself comprise a permanent magnet, an electromagnet, or a superconducting electromagnet.
In some applications it is important to have a field in a direction approximately perpendicular to the xe2x80x9cpullingxe2x80x9d direction, i.e., the gradient direction. In some instances it would further be desirable to controllably change the relationship between the gradient direction and the field direction. One way of doing this efficiently is to use a multipole magnet, such as a quadrupole magnet. In such magnets, simple translation can change the field direction 90xc2x0 while, since the gradient direction remains unchanged, changing the relationship between the field direction and the gradient direction. Another way of doing this efficiently is to use a simple magnet, and rotate it to use the side field. A simple magnet can be less expensive and stronger for a given weight than a multipole magnet, but there are occasions where the rotation required of a simple magnet might make the articulation more interfering with imaging and other medical apparatus in the surgical field.
The apparatus and method of this invention can thus provide for applying a directing magnetic field at any desired angle to a magnetic medical device within an operating region in a nearby patient, while simultaneously applying a pulling gradient in an essentially transverse direction to the orientation of the magnetic field.
The apparatus and method of this invention can also provide a method and apparatus for performing surgery on a patient by directing a magnetic medical device, such as a catheter or endoscope having a magnetic or magnetically permeable tip, in a direction perpendicular to the magnetic field. Thus, the magnetic medical device axis is easily oriented, even with modest or weak magnetic fields.
The apparatus and method of this invention can also provide an external magnet system for magnetically assisted surgery that will provide an orienting field and transverse gradient for stable and reliable movement of a magnet medical device.
The apparatus and method of the invention can also provide an external magnet system for magnetically assisted surgery using a magnetic medical device, in which the direction and strength of the magnetic force on the magnetic medical device may readily be controlled by a surgeon.
Finally, the apparatus and method of this invention can provide a magnet system for magnetically assisted surgery that minimizes the limiting effect of exclusion zones on the ability of the magnet system to provide magnetic fields of selected direction and strength within.